1. Field
The Present Invention Relates to a Semiconductor device and a method for manufacturing the semiconductor device.
2. Description of the Related Art
As illustrated in FIG. 1, in a semiconductor device, particularly, in a compound semiconductor device (Schottky gate FET) used for a high power usage, a pair of an ohmic electrode 102 and a gate electrode 103 are, for example, formed on a surface of a compound semiconductor laminated structure 101 in which an implantation area 100 is provided by a method such as an ion implantation, and an active area is fixed. An insulation film (for example, a silicon nitride film) 104 is formed so as to cover the surface of the compound semiconductor laminated structure 101 and the ohmic electrode 102.
The performance (including the reliability) of such a compound semiconductor device for high power usage largely depends on a condition of a boundary (a contacting boundary of semiconductor surface/insulation film) between the surface of the compound semiconductor laminated structure 101 and the insulation film 104 and nature of the insulation film 104 itself covering the surface of the compound semiconductor laminated structure 101.
For example, in the compound semiconductor device for high power usage, the insulation film 104 covering the surface of the compound semiconductor laminated structure 101 contacts to the gate electrode 103. Thus, a high electric field is impressed to the insulation film 104, and leak current is flowed from the gate electrode 103 to inside of the compound semiconductor laminated structure 101 through the insulation film 104. The life (reliability) of a device is influenced by this leak current. Many studies have been executed for a high-quality surface protection insulation film and to improve the life (reliability) of the device, or the like.
Additionally, the performance, which is requested for the insulation film (for example, the silicon nitride film) for the compound semiconductor device for protecting a compound semiconductor surface, includes two points of a stabilizing action for the compound semiconductor surface, and a favorable insulation characteristic of the insulation film itself.
Here, the stabilizing action for the compound semiconductor surface means such an action that, by forming the insulation film on the compound semiconductor surface, a chemical change phenomenon on the compound semiconductor surface is suppressed, and the accompanying change of surface electric potential because of the chemical change phenomenon is suppressed.
For example, the insulation film, which is excellent for the stabilizing action for the compound semiconductor surface, means the insulation film includes a lot of hydrogen (H)-terminated bond, and the like in the insulation film. Such an insulation film includes a large chemical action for the compound semiconductor surface, and in some cases, such an action is expected that an instable atomic coupling condition on the compound semiconductor surface is returned to a normal condition.
On the other hand, the favorable insulation characteristic of the insulation film itself means such a characteristic that the leak current flowed in the insulation film is small even when the high electric field is impressed. Particularly, in a SiN film, the leak current in the film is largely changed according to a chemical coupling condition between a silicon (Si) atom and a nitrogen (N) atom.
For example, the insulation film, whose insulation characteristic is favorable, means the insulation film in which every coupling arm in the insulation film is used. Since current flowed in the insulation film is very small, it is possible to suppress the leak current through the insulation film, and to reduce the change of film quality because of the current flowing in the insulation film.
However, if the stabilizing action by the insulation film for the compound semiconductor surface is not enough, the device characteristic, such as current fluctuation when the device is operated, is influenced.
If the favorable insulation characteristic of the insulation film itself is not obtained, the leak current is flowed, and the performance of the compound semiconductor device is degraded.
It is essentially difficult from a viewpoint of a chemical coupling of the insulation film to combine the two points that the stabilizing action by the insulation film for the compound semiconductor surface is improved, and the favorable insulation characteristic of the insulation film itself is obtained.